1. Field of the Invention
The present invention relates to an illuminating device to be used in a projector or the like that modulates light emitted from a light source by a light modulation device and projects the light on a screen to display an image thereon. The present invention also relates to an illuminating method using such an illuminating device. The present invention further relates to an image signal processing device and an image signal processing method, which employ the above illuminating device and the illuminating method. Still further, the present invention relates to an image projecting apparatus using the image signal processing device and image signal processing method.
2. Description of the Related Art
An image projecting apparatus such as a projector includes an illuminating device and a projector lens. The illuminating device illuminates a light modulation device such as a liquid crystal panel or DMD® (Digital Micromirror Device) with light. Then the projector lens projects the transmitted or reflected light from the light modulation device onto a screen. For the illumination optics of the related-art projector, an integrator optical system is employed to uniformly illuminate a light modulation device such as a liquid crystal panel with light from a light source. The light originally emitted from the light source has the nonuniformity of luminance. Thus, if the light is directly introduced into a light modulation device such as a liquid crystal panel, the nonuniformity of luminance is reflected on the panel and causes nonuniformity in luminance of an image projected. Therefore, for evenly projecting the image with uniform luminance, an integrator optical system that makes the luminance of light from the light source uniform has been used.
In general, the integrator optical system includes two lens arrays. The light from a light source passes through two lens arrays, followed by a light modulation device such as a liquid crystal panel being illuminated with a substantially uniform light distribution. Subsequently, the light passed through the light modulation device such as a liquid crystal panel is projected on a screen or the like by an optical projecting system, thereby projecting an image to the periphery of the screen with uniform luminance.
FIG. 1 is a schematic view illustrating an integrator optical system and its surrounding optical system in an image projecting apparatus typically used in the art. On the light path of light emitted from a light source 31 are arranged a first lens array 34, a second lens array 35, an optical system 36 including a focusing lens, a polarization converting element, and the like, and a light modulation device 37 such as a liquid crystal panel. The light emitted from the light source 31 is divided into light beams and incident on the first lens array 34. Then the divided light beams enter the second lens array 35. The light passed through the second lens array 35 is uniformly distributed and incident on the light modulation device 37 through the optical system 36 located downstream from the second lens array 35. As a result, the light beams divided by the first lens array 34 are overlapped with one another on the light modulation device 37, providing the entire light with uniform luminance.
FIG. 2 is a schematic view illustrating intensity distribution of light passing through an integrator optical system and light on the surface of a light modulation device. For instance, light with intensity a1 on the first lens of the first lens array 34 passes through the second lens array 35 and the light is then incident with intensity b1 on the light modulation device 37. Likewise, light with intensity a2 on the second lens of the first lens array 34 passes through the second lens array 35 and the light is then incident with intensity b2 on the light modulation device 37. In this manner, the light beams divided by the first lens array 34 are incident on the light modulation device 37 and then overlapped with one another, resulting in light with intensity b6 in total and almost uniform luminance from end to end of the light modulation device 37.
Japanese Unexamined Patent Application Publication No. 2007-114263 discloses a technology where light with uneven distribution of intensities emitted from a light source is converted into light with uniform distribution of intensities using two lens arrays. According to the technology disclosed in Japanese Unexamined Patent Application Publication No. 2007-114263, the production of an array of lenses with desirable shapes for the second lens array leads to overcome lacking in uniformity of light due to the configurations of the respective lenses, thereby forming an image with high luminance uniformly on the projected area of a screen or the like.